Various materials are required in the manufacture of an article of footwear. The midsoles and outsoles of an article of athletic footwear typically comprise a combination of synthetic and natural rubber, thermoplastics and thermosetting or otherwise cured plastics, and leather materials. The uppers of an article of footwear typically comprise leather, natural fibers (e.g. cotton), synthetic fibers (e.g. polyester) and the like. During the manufacture of an article of footwear, these materials are cut into a desired shape to fit a particular pattern or design. As a result of the cutting process, portions of these materials are discarded as scrap thereby increasing the cost of manufacture and indirectly harming the environment by competing for available landfill space. Also, defective and used articles of footwear currently are discarded further increasing the manufacturing costs and further burdening available landfill space.
It has been known to use discarded tire material in shoe outsoles. U.S. Pat. No. 1,687,441 to Grosjean uses waste from tire making where the waste tire material comprises cords made from cords or fabric material covered by a thin coating of uncured rubber. The cords typically are processed so that they are maintained intact while being orientated and aligned in such a fashion to impart strength to the outsole. U.S. Pat. No. 2,822,627 to Seiberling prepares blown fiber-containing shoe soles from scrap tire cord (preferably coated with uncured rubber), overshoes and hoses. The fibers in the rubber sources are aligned in the general direction in which the stock is passed through a cracker mill with corrugated rollers and then run it through a chopper with parallel blades and cut to the desired length (less than about 2 inches). U.S. Pat. No. 2,041,223 to Bollman utilizes finely divided vulcanized rubber, such as finely ground truck tires as a filler in a rubber/solvent composition. The composition hardens as the solvent evaporates and is useful in the repair of shoe soles.
U.S. Pat. No. 2,643,234 to Backus discloses a non-skid crepe rubber composition containing finely divided neoprene dissolved in a suitable solvent and to which is added ground rubber (less than 8 mesh screen size). The ground rubber source may be vulcanized or unvulcanized natural rubber, synthetic rubbers and rubber scraps. The composition may also contain fibrous fillers such as cotton fibers, leather fibers, cellulose flock and synthetic yam fibers. The fibers may be micropulverized.
It also has been known to employ fibrous materials such as cellulosic flock including silk, cotton and rayon flock materials as well as wool in the manufacture of vulcanized rubber materials to impart various characteristics to the rubber such as toughness. See U.S. Pat. Nos. 2,039,529 to Guinzburg (sheet-form rubber products containing animal or vegetable flock, such as silk or cotton, respectively, which has been reduced to a very fine, powdery condition); 2,638,457 to Gates (shoe sole composition containing cellulosic flock, e.g. cotton and rayon); 4,405,730 to Cohen (shoe sole composition comprised of polyvinyl chloride and cellulosic flock having a fiber length of from about 30 to about 300 microns).
It also has been known to employ ground or pulverized leather in the manufacture of vulcanized rubber materials to impart various characteristics to the rubber such as leather-like properties and toughness. See U.S. Pat. Nos. 1,995,179 to Holm (artificial leather from milled rubber and leather with cotton linters used for e.g. shoe soles); 4,162,996 to Panini et al. (leather-like material comprising a fiber mixture of leather fibers, synthetic polymer fibrils and cellulose fibers and a polymeric organic binder; useful for insoles and shoe supports) and 4,834,762 to Nishibori (composition useful as a sheet material containing pulverized leather mixed with a synthetic resin).
U.S. 4,866,116 to Ek et al. discloses a composition for coating, filling, binding and protection which contains rubber with a particle size of at most about 4 mm mixed with an isocyannate curable polyurethane and an aliphatic polyether glycol. The sources of rubber include waste rubber and waste rubber fires.
The methods employed in the prior art which utilize scrap materials as fillers or reinforcing matetiffs are considerably limited in use of specific filler or reinforcing materials in various amounts, and in the use of complex procedures to effect the combination of materials. In some cases, any costs which may be saved in use of scrap materials is lost in the use of additional machinery used to align the tire cord materials and other means used to effect their addition. Moreover, only specific additives can be added to the materials used to manufacture the articles of footwear, particularly athletic footwear. Furthermore, the scrap materials of the prior art were used as a filler material with varying effects, but which typically imparted little or no advantageous effects, and were utilized primarily because they also imparted minimal adverse affects and decreased costs. Thus, there exists a need whereby costs and impact on the environment can be minimized by recycling scrap materials generated during the manufacture of footwear as an additive which imparts various improved characteristics to various raw materials used in the manufacture of an article of footwear.